Label sheets are commonly available in a number of configurations for use with any number of printers. The most common type of label sheets are laminates generally consisting of a paper overlay, or multiple overlays, and an underlying release liner, joined together with an adhesive.
The underlying release liner is most commonly a lightweight paper coated on at least one side with liquid silicon that is thermally cured to provide a low adhesion surface to which the overlay is releasably bonded with the adhesive. Such liners are generally pre-manufactured by others and therefore have to be separately introduced into the label sheet manufacturing process. Additionally, since such liners are generally purchased from a separate vendor they usually contain unimaginative printing, if any, and are prohibitively expensive when ordered with custom markings. The adhesive provides a bond between the overlay and the silicone liner that is generally sufficiently strong to hold the overlay and the liner together until separation is desired. Often label sheets include several individual labels cut in the overlay.
Such traditional label sheets have been plagued by many problems when used in modern printers. Most commonly, tight turning radiuses in the sheet feed path of modern printers cause premature separation of the labels from the liner in the printer resulting in expensive repair work. Additionally, exposure of the label to the heat of a fuser in a modern laser printer often results in liquefaction of the adhesive. Such liquefied adhesive may then be expelled from between the overlay and the release liner during printing causing significant damage to expensive printing equipment. Further, silicon coated release liners are virtually impossible to print on, even when they are only coated with silicon on one side. Additionally, release liners that are silicon coated on only one side tend to curl when exposed to heat often rendering the label useless. This is particularly true when the release liner does not completely cover the overlay, as is often desired. Further, embodiments having partial release liners are further plagued by increased curling problems on the portion of the label sheet that does not contain the release liner, a problem heightened when duplex laser printers are used. Lastly, silicon coated release liners are also relatively expensive and often are difficult to introduce in the label sheet making process.
Label sheets have wide ranging application. In the pharmacy industry label sheets are utilized for pharmacy scripts whereby they have numerous uniquely sized labels for application to drug containers contained in the sheet along with several detachable sections that may serve as a customer receipt, a pharmacy order copy, as well as sections directed toward informing the customer of application instructions and potential dangers, among others. As such, a pharmacy script may easily consist of well over a dozen individual areas that require application of unique printing.
Numerous attempts have been make to overcome some of these difficulties. For example, U.S. Pat. No. 6,410,111 to Roth et al. has attempted to reduce the problem of premature separation of the overlay and the liner with the use of bond areas of varying strengths. The selective application of varying release coatings and adhesive bonds requires unique equipment and processes. U.S. Pat. No. 6,254,952 to Fox et al. introduces a leading edge feed strip to reduce the potential for premature separation caused by printer rollers. The introduction of the leading edge feed strip reduces the area available for labels and increases waste.
Traditionally, label sheet manufacturers have not produced label sheets that contain individual labels that extend all the way to the edge of the sheet due to the likelihood of premature separation, discussed above, and the issue of adhesive liquefaction. Maintaining the individual labels inward from the label sheet edges permits the manufacturer to avoid application of adhesive near the edges of the label sheet. Therefore, even if liquefaction occurs during printing, the liquefied adhesive is unlikely to be expelled from the label sheet and cause damage to the printer. This adhesive setback region results in reduced area available for labels, thereby increasing waste, and has been a limitation on the sheet label industry.
Further, manufacturers of label sheets have long recognized that the end users of the label sheets desire the ability to print indicia on both sides of a curl resistant label sheet that may have preprinted indicia on the release liner front surface and the overlay's rear surface, while using an off the shelf printer. While U.S. Pat. No. 6,304,849 to Uecker et al., attempts to solve many of the problems previously discussed, it teaches the use of a preferred printer having fewer paper feed path turns of small radius than a conventional printer, and having lower fusing temperature.
The instant invention utilizes a curl resistant single substrate to create both the overlay and the release liner, thereby overcoming many of the problems of the prior art. Manufacturing a release liner of the same material as the overlay that receives a release coat, eliminates the need for expensive silicon coated release liners and their inherent problems. Additionally, the instant invention may incorporate features designed to increase the rigidity of the label sheet, thereby reducing curling and the likelihood of printer jams. Further, such construction permits the use of a web offset lithography printing process rather than traditional label printing methods, thereby significantly improving production time, waste production, color capabilities, availability of auxiliary elements such as remoist and scratch-off areas, nesting variations, and quality.
Accordingly, the art has needed a means for improving the art of label sheets designed for use with conventional off the shelf printers, including duplex printers. While some of the prior art devices attempted to improve the state of the art, none has achieved the unique and novel configurations and capabilities of the present invention. With these capabilities taken into consideration, the instant invention addresses many of the shortcomings of the prior art and offers significant benefits heretofore unavailable. Further, none of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.